Whenever you’re thinking about buying an air compressor or pneumatic tools, there are a number of important specifications that you will need to consider.
One of them is air compressor CFM, or Cubic Feet per Minute.
This specification is important not just for determining the use of a compressor, but for determining if a particular compressor is suitable for the jobs that you want to accomplish. This could be in relation to the tools that you already have, or even the tools that you are thinking about buying.
You can think of air compressor CFM as a measure of the maximum airflow that the compressor is capable of. As you can imagine, air compressor CFM requirements vary depending on the tool.
A heavy duty sander requires a high CFM air compressor, whereas a brad nailer requires significantly less. Let’s take a look at the requirements of the most common pneumatic tools, and how you can make sure you choose the right compressor for the job.
Why Air Compressor CFM Measurements are Important
Quite simply, CFM measures the air that is able to flow through any particular device. In this case, the device is the air compressor. Understanding the CFM output of the compressor alone is not enough, because the tools you use with it will have their own specific CFM requirements.
Higher CFM means that more energy can be applied to the movement of a tool. This is why a continuously articulating tool like a sander, spray gun, or even pneumatic shears, require higher CFM figures. The pressure of the compressed air is also important to powering a pneumatic tool, and most consumer and ‘prosumer’ grade tools are based on CFM measured at 90 PSI.
It’s important not to confuse CFM with the storage capacity of an air compressor. CFM can measure the maximum flow rate of the air released from a compressor, whereas the tank capacity of a compressor determines how much air can be stored. The relationship is that a high CFM air compressor generally has a larger tank, because this allows for the flow rate to be maintained over longer durations.
Buying tools and Compressors based on Air Flow
You now know how CFM relates to the output of an air compressor, and you know that air tool CFM requirements are different depending on certain tools. To give you an idea of how you’re going to go shopping, take a quick look at three popular portable air compressors and how they stack up when it comes to CFM.
- The Senco PC1010 is a 1hp portable compressor with a peak CFM of 0.7
- The DeWalt DWFP55126 is a slightly larger portable compressor that is capable of up to 2.6 CFM
- At the other end of the portable scale is the Ingersoll-Rand Garage Mate, which produces an impressive 5.5 CFM.
Check below to get the latest price and offers on Amazon for this air compressor model.
Now looking at these units you might immediately assume the Senco to be an inferior product, however a CFM rating doesn’t tell the full story, especially considering that 0.7 CFM can be more than capable for some lightweight tasks.
Air Tool CFM Requirements @ 90 PSI
This is a handy list containing the CFM @ 90 PSI ratings of the most commonly used air tools:
|Air Tool||CFM Rating|
|Brad Nailer for smaller finishing jobs||0.3|
|3/8 " Impact Wrench||2.5 - 3.5|
|Pneumatic Hammer (varying sizes)||3 - 11|
|Pneumatic Chisel (varying sizes)||3 - 11|
|Pneumatic Drill||3 - 6|
|Hydraulic Riveting Gun||4|
|1/2 " Impact Wrench||4 - 5|
|Die Grinder (small)||4 -6|
|Pneumatic Speed Saw||5|
|Orbital Sander||6 - 9|
|Upholstery / Industrial Sears||8 - 16|
|Rotational Sander||8 -12.5|
If you’re looking for comprehensive data on average CFM ratings for power tools, check out the Engineering Toolbox.
Taking these figures in to account, you might assume that the previously mentioned 0.7 CFM compressor would be perfect for brad nailing, and you would be correct, however this isn’t to say that the Ingersoll-Rand Garage Mate would be sufficient for continuously running a Pneumatic Speed Saw.
To understand why, you need to learn how manufacturers determine these ratings. It’s standard practice in the industry to advertise an average CFM rating. What is widely accepted as average is a 25% running (or duty) cycle. This means that the tool will be in use for 15 seconds of any given minute.
In the case of a hydraulic riveting gun, a grease gun, or even a ½” Impact Wrench, a 5.5 CFM air compressor would be sufficient. This is because these tools are only used intermittently, so you can assume that they wouldn’t exceed the average 25% running cycle.
Now alternatively, consider the Pneumatic Speed Saw running from the same 5.5 CFM air compressor. Because the speed saw is likely to be run continuously for more than 15 seconds of every minute, its requirement of 5CFM needs to be multiplied by up to 4x. Unless the saw was being used intermittently, the Ingersoll-Rand Garage Mate wouldn’t be able to provide an adequate flow rate.
This example shows just how important it is to ensure you match your tools and your air compressor. It also shows why choosing a modestly powered compressor for your current needs could limit the versatility of your compressor.
The vast majority of the most popular tools require between 2 and 4 CFM to operate, so unless you are using a compressor for specialized lightweight tasks like inflating or airbrush detailing, then it’s likely you’re going to need a compressor with at least 2 CFM @ 90PSI.
Here’s a video that may help you to better understand these concepts.
SCFM vs CFM
Since we’re talking about air compressor CFM, we need to address the confusion that exists when manufacturers release compressors that are rated with SCFM. The difference between these two similar acronyms is that SCFM should be a standard measurement. It indicates Standard Cubic Feet per Minute. This means that SCFM ratings are measured in identical conditions, using identical equipment. As a buyer, the difference won’t impact you. A manufacturer could implement their own ‘standard’ CFM rating, but this may differ to another company’s method. So if you’re comparing CFM on one tool or compressor to another that is rated using SCFM, you can think of them in the exact same context.
You Can’t Ignore CFM When Purchasing a New Air Compressor
The CFM value of any air compressor is directly responsible for the tools that it will be able to power. When looking for a new compressor, choose one that satisfies your current requirements, but consider your future needs as well.
Always check the requirements when you’re buying a new air tool, and remember that continuous run tools require figures up to 4x that of their rated CFM figure. In this way you can ensure that you’re ready for inflating tires on your car, finishing off some interior trim with your brad nailer, or even speeding through automotive work with a ½” impact wrench.